The overall objective of this project is to develop in vitro methods to the point that biochemical techniques could be used in the analysis of mutants which block the development on imaginal discs of Drosophila melanogaster. We have found that the imaginal discs in at least two of our mutants readily establish cell lines "in vivo" and we have developed a satisfactory screening procedure for media which could support "in vitro" proliferation. Our plans include testing a large number of compounds which support growth of other kinds of cells, for example, a wide variety of sera, synthetic polymers, vitamins, cyclic nucleotides, etc. Two kinds of experiments will be conducted using the optimal conditions we have established for "in vitro" differentiation. Imaginal discs from specific mutants will be allowed to differentiate "in vitro" and the results will be commpared to those obtained when the same discs were cultured "in vivo". We will also use a scaled up version of this system using mass isolated discs to begin examining biochemical parameters of the differentiation of normal discs.